This research project is designed to purify human renal renin from cadaver kidney in order to: 1) characterize human renin as an enzyme and protein, 2) to develop a direct radioimmunoassay for renin to clarify its role in the pathogenesis of human hypertension, and 3) to study the relationship of renin to its precursor form(s). The past year has witnessed the complete purification of human renal renin with satisfaction of certain of the biochemical criteria for homogeneity. The product of this purification represents, to our knowledge, the only existing preparation of pure human renin reported to date. We plan, based upon the above purification 1) to effect purification of human renal renin in large scale, 2) to determine the exact molecular weight and isoelectric point of human renal renin, 3) to initiate amino acid and amino terminal sequence analyses, 4) to achieve production of antibody to pure human renal renin, 5) to purify this antibody for the development of a direct radioimmunoassay for human renal renin, and 6) to use this antibody for studies concerning the relationship of renin to its precursor form(s). Not until huma renin is purified in large scale can its role in the pathogenesis of hypertension be fully understood. Insight gained into the mechanism of renin action will offer the potential for new approaches in the therapy of human hypertension.